The reducible cross-links in the high molecular weight protein fraction of normal and cataractous human lenses will be reduced and labeled with NaB3H4. The labeled cross-links will be released by acid hydrolysis and identified by elution from ion exchange column. The labeled cross-linked peptides will be released by proteolysis and separated by gel and ion-exchange chromatography, and analyzed for amino acid composition and polypeptide chains. The transglutaminase activity of rat and human lenses will be determined in lens homogenate and in the intact lens in culture, in the presence and absence of calcium ionophore. The polymerizing activity of transglutaminase will also be assessed. The presence of gamma-(glutamyl)-epsilon-lysyl dipeptides in the composition of high molecular weight proteins from normal and cataractous human lenses will be determined, after proteolysis followed by ion-exchange chromatography. The transglutaminase catalyzed incorporation of biologically and pharmacologically active amines, e.g., histamine, seratonin, dopamine and amphetamine, into the lens proteins will be investigated, and the effect on the aggregation of crystallins will be assessed.